1. Field
Embodiments of the present invention relate to an electric parking brake system which is mounted to a vehicle and is operated by a motor.
2. Description of the Related Art
Generally, a parking brake system is a system to stop a vehicle so as not to move when parking the vehicle. The parking brake system serves to catch a wheel so as to prevent rotation of the wheel.
FIG. 1 is a sectional view illustrating a partial configuration of a vehicle having a conventional manual parking brake system.
Referring to FIG. 1, the conventional manual parking brake system includes a drum 1 which is rotated along with a vehicle wheel, and a first brake shoe 2 and a second brake shoe 3 which are mounted within the drum 1 and apply brake force to the drum 1 via friction with an inner surface of the drum 1. Additionally, an operating lever 5 is provided in the drum 1. The operating lever 5 pushes the two brake shoes 2 and 3 against the inner surface of the drum 1 when a parking cable 4, connected to a parking lever provided at the driver's seat, is pulled.
The first and second brake shoes 2 and 3 respectively include rims 2a and 3a, which are bent in a semicircular form to correspond to the inner surface of the drum 1, linings 2b and 3b attached to outer surfaces of the rims 2a and 3a via friction with the inner surface of the drum 1, and webs 2c and 3c coupled to inner surfaces of the rims 2a and 3a to reinforce the rims 2a and 3a. 
The operating lever 5 includes a support lever 6, a pressure member 7, and a pivoting lever 8. The support lever 6 has one end to support the web 2c of the first brake shoe 2, and the other end of the support lever 6 is extended toward the second brake shoe 3. The pressure member 7 is coupled to the support lever 6 so as to be reciprocally movable in a longitudinal direction of the support lever 6. One end of the pressure member 7 is supported by the web 3c of the second brake shoe 3. The pivoting lever 8 is pivotally coupled to the support lever 6. The pivoting lever 8 is pivoted when the parking cable 4 is pulled, thereby acting to push the pressure member 7.
One end of the pivoting lever 8 is pivotally coupled to the support lever 6 via a pivot shaft 8a, and the other end of the pivoting lever 8 penetrates a back-plate 10 to protrude outward. An end of the pivoting lever 8 protruding outward of the back-plate 10 is provided with a hook 8b such that the parking cable 4 is caught by the hook 8b to thereby be connected to the pivoting lever 8.
The other end of the pressure member 7 comes into contact with the pivoting lever 8 and contact portions of the pressure member 7 and the pivoting lever 8 have a concavely curved surface form.
In operation of the above described parking brake system, when the parking cable 4 connected to a parking lever (not shown) of the driver's seat is pulled, the pivoting lever 8 is pivoted in a direction designated by the arrow A about the pivot shaft 8a, so that the curved surface portion of the pivoting lever 8 applies pressure to the curved surface portion of the pressure member 7. Thereby, the pressure member 7 acts to push the web 3c of the second brake shoe 3 against the inner surface of the drum 1. At the same time, the support lever 6 is advanced toward the first brake shoe 2 by reaction acting on the support lever 6, thereby pushing the web 2c of the first brake shoe 2. As a result, the two brake shoes 2 and 3 come into close contact with the inner surface of the drum 1, thereby applying brake force to the drum 1.
Meanwhile, not-described reference numeral ‘9’ is a return spring that returns the two brake shoes 2 and 3 to their original positions when the brake force is removed.
In the case of the above described conventional parking brake system, the pivoting lever 8 is rotated when the parking cable 4 is pulled and pressure is applied to the second brake shoe 3 via rotation of the pivoting lever 8. Therefore, as the second brake shoe 3 pushes the pivoting lever 8 in a rotating direction thereof, the second brake shoe 3 is moved in a braking direction, thereby generating brake force.
However, the above described conventional parking brake system requires a driver to inconveniently pull the parking lever with appropriate force. Further, the parking lever has a large operating radius, which may deteriorate use of the interior space of a vehicle.
In consideration of the aforementioned inconvenience of the manual parking brake system, an electric parking brake system to automatically operate a brake using a motor has been proposed. Recently, a variety of research and development to achieve utility of an installation space, enhanced operating performance, operating noise reduction, and the like has been conducted.